PubMed Health⌕ Search

Biomedical subjects

X H Zhu

Publications and source records attributed to X H Zhu.

At least 19 recordsLinked to original sources
PubMed2003

Study of a mathematical model of metal ion complexes in solvent sublation.

Separation of metal ion complex, [(C(12)H(8)N(2))(3)Fe(2+)], with surfactant sodium dodecylphrate (DLS) complex from aqueous phase was carried out by solvent sublation, which obeys first-order kinetics. On the base of the complete transport mechanisms, the Langmuir adsorption, and the ion complex equilibrium in the aqueous phase, a mathematical model for the [(C(12)H(8)N(2))(3)Fe(2+)]-surfactant ion complex is obtained with the aid of the Mathematic 4.0 program, 4th Runge-Kutta method, and the Matlab programs. The effects of many parameters, such as K(a), K(l), K(ow), d(i), V(o), V(w), and Q(a), on solvent sublation are investigated. Furthermore, the simulation showed that the model is substantiated for experiments on the solvent sublation of the complex.

Journal Article↗
PubMed2001

Correlation of activation sizes between lateral geniculate nucleus and primary visual cortex in humans.

It is well established that the lateral geniculate nucleus (LGN) and the primary visual cortex (V1) are retinotopically organized. This similarity is expected to reflect a correlation of activation sizes between V1 and LGN during visual stimulation. However, it is a challenge to determine this functional correlation experimentally in the human brain using most neuroimaging techniques due to their low sensitivity for detecting small LGN activation in the thalamus. The purpose of this study was to examine the functional correlation of activation sizes between LGN and V1 during fullfield and hemifield visual stimulation using a large visual field and high-resolution fMRI technique at 4 Tesla. The correlation was determined by comparing the V1 and LGN activation size ratios between the left and right hemispheres of the same subjects. The results reveal 1) a linear correlation of functional activation size ratio between LGN and V1 with a correlation coefficient of 0.96, and 2) the capability of fMRI for quantifying spatial correlation between cortical and subcortical activation. Magn Reson Med 45:202-205, 2001.

Geniculate Bodies↗
PubMed2001

Study of tricarboxylic acid cycle flux changes in human visual cortex during hemifield visual stimulation using (1)H-[(13)C] MRS and fMRI.

The relationships between brain activity and accompanying hemodynamic and metabolic alterations, particularly between the cerebral metabolic rate of oxygen utilization (CMR(O2)) and cerebral blood flow (CBF), are not thoroughly established. CMR(O2) is closely coupled to the rate of tricarboxylic acid (TCA) cycle flux. In this study, the changes in glutamate labeling during (13)C labeled glucose administration were determined in the human brain as an index of alterations in neuronal TCA cycle turnover during increased neuronal activity. Two-volume (1)H-[(13)C] MR spectroscopy (MRS) of the visual cortex was combined with functional MRI (fMRI) at 4 Tesla. Hemifield visual stimulation was employed to obtain data simultaneously from activated and control regions located symmetrically in the two hemispheres of the brain. The results showed that the fractional change in the turnover rate of C4 carbon of glutamate was less than that of CBF during visual stimulation. The fractional changes in CMR(O2) (Delta CMR(O2)) induced by activation must be equal to or less than the fractional change in glutamate labeling kinetics. Therefore, the results impose an upper limit of approximately 30% for Delta CMR(O2) and demonstrate: 1) that fractional CBF increases exceed Delta CMR(O2) during elevated activity in the visual cortex, and 2) that such an unequal change would explain the observed positive blood oxygenation level dependent (BOLD) effect in fMRI. Magn Reson Med 45:349-355, 2001.

Blood Glucose↗
PubMed2001

17O relaxation time and NMR sensitivity of cerebral water and their field dependence.

17O spin relaxation times and sensitivity of detection were measured for natural abundance H(2)(17)O in the rat brain at 4.7 and 9.4 Tesla. The relaxation times were found to be magnetic field independent (T(2) = 3.03 +/- 0.08 ms, T(*)(2) = 1.79 +/- 0.04 ms, and T(1) = 4.47 +/- 0.14 ms at 4.7T (N = 5); T(2) = 3.03 +/- 0.09 ms, T(*)(2) = 1.80 +/- 0.06 ms, and T(1) = 4.84 +/- 0.18 ms at 9.4T (N = 5)), consistent with the concept that the dominant relaxation mechanism is the quadrupolar interaction for this nucleus. The (17)O NMR sensitivity was more than fourfold higher at 9.4T than at 4.7T, for both the rat brain and a sodium chloride solution. With this sensitivity gain, it was possible to obtain localized (17)O spectra with an excellent signal-to-noise ratio (SNR) within 15 s of data acquisition despite the relatively low gyromagnetic ratio of this nucleus. Such a 15-s 2D (17)O-MRS imaging data set obtained for natural abundance H(2)(17)O in the rat brain yielded an SNR greater than 40:1 for a approximately 16 microl voxel. This approach was employed to measure cerebral blood flow using a bolus injection of H(2)(17)O via one internal carotid artery. These results demonstrate the ability of (17)O-MRS imaging to reliably map the H(2)(17)O dynamics in the brain tissue, and its potential for determining tissue blood flow and oxygen consumption rate changes in vivo. Magn Reson Med 45:543-549, 2001.

Animals↗
PubMed2001

Observed BOLD effects on cerebral metabolite resonances in human visual cortex during visual stimulation: a functional (1)H MRS study at 4 T.

Using the localized spin-echo (1)H MRS technique, the water resonance and methyl resonance peaks of the cerebral metabolites N-acetylaspartate (NAA at 2.0 ppm) and phosphocreatine/creatine (Cr at 3.0 ppm) were studied in the human visual cortex to detect and quantify the blood oxygenation level dependent (BOLD) effect during visual stimulation at 4 T. Significant BOLD effects, which reflect the increases of spectral peak height (H) accompanied by the decreases of spectral linewidth (Deltaupsilon(1/2)), were observed in NAA (H: 2.5%; Deltaupsilon(1/2): -1.7%) and Cr (H: 3.1%; Deltaupsilon(1/2): -1.8%) as well as in water (H: 3.1%; Deltaupsilon(1/2): -2.3%). Because NAA and Cr mainly exist in the brain cells, the BOLD effects on these cerebral metabolite resonances only measure the susceptibility component spreading into the extravascular cellular compartment. In contrast, water is affected in the intra- and the extravascular compartments. Therefore, the water signal measures the BOLD effects in both compartments. BOLD responses in water were similar to those observed in metabolites. The similarity indicates that the susceptibility spreading into the extravascular parenchyma contributed significantly to the observed BOLD effects at 4 T. Finally, taking advantage of the higher NMR sensitivity at 4 T, the feasibility of measuring BOLD effects on cerebral metabolites by localized (1)H MRS is demonstrated.

Adult↗
PubMed2001

The effect of stimulus-response compatibility on cortical motor activation.

Stimulus-response compatibility (SRC) is a general term describing the relationship between a triggering stimulus and its associated motor response. The relationship between stimulus and response can be manipulated at the level of the set of stimulus and response characteristics (set-level) or at the level of the mapping between the individual elements of the stimulus and response sets (element-level). We used functional magnetic resonance imaging (fMRI) to investigate the effects of SRC on functional activation in cortical motor areas. Using behavioral tasks to separately evaluate set- and element-level compatibility, and their interaction, we measured the volume of functional activation in 11 cortical motor areas, in the anterior frontal cortex, and in the superior temporal lobe. Element-level compatibility effects were associated with significant activation in the pre-supplementary motor area (preSMA), the dorsal (PMd) and ventral (PMv) premotor areas, and the parietal areas (inferior, superior, intraparietal sulcus, precuneus). The activation was lateralized to the right hemisphere for most of the areas. Set-level compatibility effects resulted in significant activation in the inferior frontal gyri, anterior cingulate and cingulate motor areas, the PMd, PMv, preSMA, the parietal areas (inferior, superior, intraparietal sulcus, precuneus), and in the superior temporal lobe. Activation in the majority of these areas was lateralized to the left hemisphere. Finally, there was an interaction between set and element-level compatibility in the middle and superior frontal gyri, in an area co-extensive with the dorsolateral prefrontal cortex, suggesting that this area provided the neural substrate for common processing stages, such as working memory and attention, which are engaged when both levels of SRC are manipulated at once.

Adult↗
PubMed2001

The kinetics and thermodynamics of surfactants in solvent sublation.

Solvent sublation has been performed on very dilute solutions of one cationic surfactant, hexadecylpyridinium chloride (HPC), and one anionic surfactant, dodecylbenzenesulfonic acid (LBS). Some thermodynamic values were obtained, e.g. molecular areas, A0, which are 50.0 and 47.7 A2/molecule, respectively, for HPC and LBS, and free adsorption energies, delta G(o)ads, which are -33.17 and -43.58 kJ mol(-1), respectively, for HPC and LBS. The kinetics were determined for a range of temperatures and gas flow-rates. Although the processes of solvent sublation of the two surfactants obey first-order kinetics, the respective adsorption mechanisms of HPC and LBS in the solvent sublation process were different. The pH and the presence of KCl and ethanol had no effect on the solvent sublation of LBS. The apparent active energy was calculated as 8.11 kJ mol(-1).

Journal Article↗
PubMed2001

Withanolide-type steroids from Solanum cilistum.

Six withanolide-type steroids, named as cilistols a, b, d, q, g and f, respectively, were isolated from the leaves of Solanum cilistum. The major component among them, cilistol a, was characterized as (22R, 24S, 25R, 26R)-1-oxo-22, 26; 24, 25-diepoxy-17alpha, 26-dihydroxyergost-2,5-diene on the basis of spectroscopic properties and X-ray crystallographic analysis; the other isolated compounds had closely related structures. This is the first report of withanolide-type steroids in the Solanum genera.

Ergosterol↗
PubMed2001

Enhancing 1 alpha-hydroxylase activity with the 25-hydroxyvitamin D-1 alpha-hydroxylase gene in cultured human keratinocytes and mouse skin.

1 alpha,25-Dihydroxyvitamin D(3) (1 alpha,25(OH(2))D(3)) and its analogs are used to treat psoriasis because of their potent antiproliferative activity. They have the potential for causing hypercalcemia, however, and patients often become resistant to the drug. We examined the feasibility of enhancing the cutaneous production of 1 alpha,25(OH(2))D(3) using a human 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-OHase) plasmid. The 1 alpha-OHase gene was fused to the green fluorescent protein gene (1 alpha-OHase-GFP) driven by the cytomegalovirus promoter. Transfection of cultured normal human keratinocytes with the 1 alpha-OHase-GFP plasmid resulted in a marked increase in the expression of 1 alpha-OHase-GFP in the mitochondria. Transfection of keratinocytes with 1 alpha-OHase-GFP or 1 alpha-OHase plasmids in vitro enhanced the 1 alpha-OHase activity substantially and increased the sensitivity of the keratinocytes to the antiproliferative effect of 25(OH)D(3). The 1 alpha-OHase-GFP plasmid was topically applied to shaved C57/BL6 mice. Twenty-four hours after topical application, immunohistochemical analysis of the skin for 1 alpha-OHase-GFP revealed the presence of 1 alpha-OHase-GFP in the epidermis and epidermal appendages including the hair follicles. The results from this study offer a unique new approach for the topical treatment of hyperproliferative disorders such as psoriasis and skin cancer using the 1 alpha-OHase gene that could locally increase the production of 1 alpha,25(OH(2))D(3) without causing hypercalcemia or resistance.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed2001

Four novel withanolide-type steroids from the leaves of Solanum cilistum.

Four novel withanolide-type steroids named cilistols p, pm, p1 and u (1-4, respectively), were isolated from the leaves of Solanum cilistum. The respective structures were characterized by spectroscopic means as follows: cilistol p (1) was (22R,24R,25R,26S)-1-oxo-22,26-epoxy-3alpha,5alpha-cycloergostane-6beta,17alpha, 24,25,26-pentaol 26-O-beta-D-glucopyranoside, cilistol pm (2) corresponded to the 6-O-methyl ether derivative of 1; cilistol p1 (3) was represented as the 24-O-methyl ether of 1, and cilistol u (4) was shown to be the epoxide between C-24 and -25, presumably bearing cilistols p, pm and p1 by ring-opening.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Six new withanolide-type steroids from the leaves of Solanum cilistum.

Six new withanolide-type steroids, designated cilistols v, t, i, j, y and w (1-6, respectively), were obtained from the leaves of Solanum cilistum. Their respective structures were characterized by spectroscopic means as follows: Cilistol v (1) was (22R,24Z)-1alpha,3beta,22,26-tetrahydroxyergost-5,24-diene 26-O-beta-D-glucopyranoside, which is regarded as the precursor of other withanolide-type steroids included in this title plant. Cilistol t (2) was (22R,24S,25R,26S)-24,25;22,26-diepoxy-1alpha,3beta,26-trihydroxyergost-5-ene 26-O-beta-D-glucopyranoside, and cilistols j (3) and i (4) corresponded to the substances probably formed by the cleavage of the epoxy ring at C-24 and 25 of 2. Cilistol y (5) was 3-O-sulphonyl (22R,24S,25R,26R)-1-oxo-24,25; 22,26-diepoxy-3beta,17alpha,26-trihydroxyergost-5-ene 26-O-beta-D-glucopyranoside, and cilistol w (6) corresponded to the substance obtained by the fission of the epoxy ring at C-24 and 25 of 5. The occurrence of these withanolide type steroids from Solanum genera is rare and worthy of note.

Ergosterol↗
PubMed2000

[The efficacy of the native flumazenil for acute poisoning with benzodiazepines].

OBJECTIVE: To evaluate the efficacy of the native flumazenil for acute self-poisoning with benzodiazepines. METHODS: One hundred and twenty-six patients with unconsciousness from benzodiazepines-induced self-poisoning were randomly divided into two groups: flumazenil group(Group II, 63 cases) were treated with flumazenil, and conventional-medicine group(Group I, 63 cases) with placebo(glucose, vitamin C, KCl). A modified Glasgow Coma Scale(MGCS) and Observer's Assessment of Alertness/Sedation Scale(OAA/S) were used in the assessment of consciousness. RESULTS: MGCS were increased by 5.3, 8.0, 9.4 and 7.3 at 15 min, 30 min, 60 min and 180 min after intravenous flumazenil(P < 0.01) and by 5.2, 7.7, 8.7 and 6.9 in comparison with conventional-medicine group(P < 0.01). OAA/S increased by 1.9 compared with conventional-medicine group(P < 0.01). No severe side-effects were found in the treatment. CONCLUSIONS: Flumazenil might improve benzodiazepines-induced unconsciousness markedly and may be the most effective antagonist of benzodiazepines.

Adolescent↗
PubMed2000

An approach to probe some neural systems interaction by functional MRI at neural time scale down to milliseconds.

In this paper, we demonstrate an approach by which some evoked neuronal events can be probed by functional MRI (fMRI) signal with temporal resolution at the time scale of tens of milliseconds. The approach is based on the close relationship between neuronal electrical events and fMRI signal that is experimentally demonstrated in concurrent fMRI and electroencephalographic (EEG) studies conducted in a rat model with forepaw electrical stimulation. We observed a refractory period of neuronal origin in a two-stimuli paradigm: the first stimulation pulse suppressed the evoked activity in both EEG and fMRI signal responding to the subsequent stimulus for a period of several hundred milliseconds. When there was an apparent site-site interaction detected in the evoked EEG signal induced by two stimuli that were primarily targeted to activate two different sites in the brain, fMRI also displayed signal amplitude modulation because of the interactive event. With visual stimulation using two short pulses in the human brain, a similar refractory phenomenon was observed in activated fMRI signals in the primary visual cortex. In addition, for interstimulus intervals shorter than the known latency time of the evoked potential induced by the first stimulus ( approximately 100 ms) in the primary visual cortex of the human brain, the suppression was not present. Thus, by controlling the temporal relation of input tasks, it is possible to study temporal evolution of certain neural events at the time scale of their evoked electrical activity by noninvasive fMRI methodology.

Animals↗
PubMed2000

[Analysis of retinoic acid in subretinal fluid in patients with rhegmatogenous retinal detachment].

To investigate the relationship between the level of retinoic acid (RA) in the subretinal fluid (SRF) and the extent of the vitreoretinopathy in 56 patients with rhegmatogenous retinal detachment, we studied the levels of RA in both SRF and serum using high liquid chromatography and also examined those levels in part of patients who took oral vitamin A 150,000 U.d-1. The results were that the level of RA in the SRF increased with the grade of the proliferative vitreoretinopathy (PVR); the levels of RA in both SRF and serum were significantly higher in the cases with vitamin A than those without. We conclude that retinoic acid metabolism between retinal pigment epithelial cells and neural epithelia was unbalanced after retinal detachment. Oral vitamin A is helpful to inhibit the genesis and development of the proliferative vitreoretinopathy.

Adolescent↗
PubMed2000

Magnetic resonance studies of brain function and neurochemistry.

In the short time since its introduction, magnetic resonance imaging (MRI) has rapidly evolved to become an indispensable tool for clinical diagnosis and biomedical research. Recently, this methodology has been successfully used for the acquisition of functional, physiological, and biochemical information in intact systems, particularly in the human body. The ability to map areas of altered neuronal activity in the brain, often referred to as functional magnetic resonance imaging (fMRI), is probably one of the most significant recent achievements that rely on this methodology. This development has permitted the examination of functional specialization in human and animal brains with unprecedented spatial resolution, as demonstrated by mapping at the level of orientation and ocular dominance columns in the visual cortex. These functional imaging studies are complemented by the ability to study neurochemistry using magnetic resonance spectroscopy, allowing the determination of metabolic processes that support neurotransmission and neurotransmission rates themselves.

Animals↗
PubMed2000

Anti-herpes virus activity of Solanum steroidal glycosides.

Since some Solanum-genus plants have traditionally been used for anti-cancer and anti-herpes agents from olden times, we examined anti-herpes simplex virus type 1 (HSV-1) activity of typical steroidal glycosides with the frameworks of spirostane (including nuatigenin glycoside), furostane, solasodane, tomatidane and ergostane (including dimer) obtained from Solanum plants. Among these steroidal glycosides, the spirostanol glycosides were most effective. An inclination was observed for the potency of activity to decrease in the order of spirostane, tomatidane, ergostane, solasodane, nuatigenin type, dimer of ergostane and furostane. It was also suggested that the activity depends on the kind of oligosacchride moiety.

Animals↗